<!DOCTYPE html>
<html lang="en">

<head>

    <meta charset="UTF-8">

    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>红绿灯</title>

    <script src="https: //cdnjs.cloudflare.com/ajax/libs/gsap/3.9.1/gsap.min.js"></script>

    <script src="https: //libs.baidu.com/jquery/2.1.4/jquery.min.js"></script>
    <style>
        @import url('https://fonts.googleapis.com/css?family=Muli&display=swap');

        * {
            box-sizing: border-box
        }

        body {
            background-color: #1abc9c;
            display: flex;
            align-items: center;
            justify-content: center;
            min-height: 100vh;
            margin: 0
        }

        .container {
            background-color: #2c3e50;
            border-radius: 50px;
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: space-around;
            padding: 15px 0;
            height: 200px;
            width: 70px
        }

        .circle {
            background-color: rgba(0, 0, 0, 0.3);
            border-radius: 100%;
            position: relative;
            height: 40px;
            width: 40px
        }

        .circle::after {
            border-right: 4px solid rgba(255, 255, 255, 0.6);
            border-radius: 100%;
            content: ' ';
            position: absolute;
            top: 5px;
            left: 0px;
            width: 30px;
            height: 30px
        }

        .circle.red {
            background-color: #c0392b;
            box-shadow: 0 0 20px 5px #c0392b
        }

        .circle.yellow {
            background-color: #f1c40f;
            box-shadow: 0 0 20px 5px #f1c40f
        }

        .circle.green {
            background-color: green;
            box-shadow: 0 0 20px 5px green
        }
    </style>
</head>

<body>
    <div class="container">
        <div class="circle red" color="red"></div>
        <div class="circle" color="yellow"></div>
        <div class="circle" color="green"></div>
    </div>
</body>
<script>
    const circles = document.querySelectorAll('.circle')
    let activeLight = 0;
    setInterval(() => { changeLight() }, 1000);
    function changeLight() {
        circles[activeLight].className = 'circle';
        activeLight++;
        if (activeLight > 2) {
            activeLight = 0
        }
        const currentLight = circles[activeLight]
        currentLight.classList.add(currentLight.getAttribute('color'))
    }
</script>

</html>